There are many circumstances in which it is desirable to encapsulate a substrate with some kind of protective barrier. In some circumstances, encapsulation can be used to protect the substrate from the environment in which the substrate will be used. For example, encapsulation is useful when the substrate is a metal component or the like that is to be used in a marine environment where salt water or the corresponding vapor or mist can corrode or otherwise damage the unprotected component. Encapsulation can also be used to protect processing equipment to be used in acidic, basic, reducing, or oxidizing environments.
In other circumstances, it may be desirable to protect items in the environment from the substrate itself. For instance, one step of manufacturing microelectronic devices involves processing those devices while the devices are supported upon some kind of structure, such as a wafer cassette, platform, transport apparatus, rotating turntable, and/or the like. For strength, rotating turntables and other structures used to process microelectronic devices are often formed from one or more metals, metal alloys, intermetallic compositions, or the like. Unfortunately, metal ions from such metallic structures can migrate from the structures into the devices being processed. This is especially problematic in the manufacture of semiconductor devices, where metal contamination of the devices can impair or even destroy the functional capability of the devices. To protect microelectronic devices from contamination during processing, the industry has encapsulated one or more components of the processing equipment in an inert polymer, e.g., a fluoropolymer such as perfluoroalkoxy polymer (PFA), a fluoroethylene polymer (FEP), an ethylene tetra fluoroethylene polymer, (ETFE), a polyvinylidene fluoride polymer (PVDF), a polyvinyl fluoride polymer (PVF), combinations of these, and the like.
To encapsulate a particular structure with an inert polymer, one or more encapsulating parts may be preformed and then assembled around the structure. The parts may be joined using glue, fusing techniques, or the like. In the microelectronics industry, the encapsulating joints must be strong enough so that the encapsulated structure can withstand the rigors of use over a reasonably long service life. If the substrate comprises metal, the encapsulation joint should be impermeable to metal ions.
Forming encapsulating joints that meets the stringent demands of the microelectronic industry has been extremely challenging. The difficulty is due, at least in part, to the complex geometry of the structures that require encapsulation. For example, the MERCURY.RTM. centrifugal spray processors commercially available from FSI International, Chaska, Minn., each includes an encapsulated, rotating turntable that supports several wafer cassettes during processing. This turntable has projecting, upright structures that help hold the wafer cassettes, and these make it difficult to satisfactorily bond encapsulating elements over the turntable to effectively seal the major faces and sidewall of the turntable. For example, as shown in FIG. 1, such a turntable (a) is schematically shown as being encapsulated by a first cover (b) fitted over the top face (c) of the turntable (a) and a second cover (d) fitted over the bottom face (e) of the turntable. The encapsulating joint between the two covers (b) and (d) is formed by placing a sideband (f) around the sidewall (g) of turntable (a) and then fusing the first and second covers (b) and (d) to this sideband (f) via welding beads (h).
It is very time-consuming, and thus very expensive in terms of manufacturing cost, to provide a satisfactory encapsulating joint between major face cover elements when using the approach of FIG. 1. What is needed is a better, more efficient way to encapsulate this kind of structure.